The present invention relates to electrical connectors. The invention has particular application to battery terminal clamps, especially to clamp adapters for side-terminal batteries.
Various types of connectors have been used for electrically connecting to battery terminals. However, traditional battery clamps are often difficult to position on side-terminal batteries. Because of this, various side-terminal adapters have been designed to connect to this type of terminal and allow easier use of traditional battery clamps. Likewise, specialized side-terminal clamps have also been designed specifically for dealing with side-terminal batteries. Examples of battery terminal connectors and side-terminal adapters are shown in U.S. Pat. Nos. 1,651,294; 2,267,826; 3,745,516; 4,377,317; 4,565,414; 5,662,504 and 5,862,515.
The prior art side-terminal adapters and battery clamps were often designed with two pivoting toothed jaws biased closed to grip a terminal therebetween. The teeth used in this design often provide minimal electrical contact with the side terminals and could easily inadvertently fall off.
Some side-terminal adapters provided a metal plate with a slotted opening between two relatively stationary toothed jaws. With this type of device, the side-terminal bolts are wedged in the opening between the jaws. However, this design tends to fail because the jaws can bend away from one another, especially when the device is attached and removed during repeated use. This bending can cause the quality of both the physical and electrical connections to deteriorate. Furthermore, any attempt to engage too large a terminal with the side-terminal adapter can permanently deform this type of device and render it useless.
Various types of circuitry and connectors have been used to make Kelvin connections that are often used for battery testing equipment. The minimal electrical contacts of prior battery clamps and side-terminal adapters become even more of a problem when a Kelvin connection is needed to test a battery. A Kelvin connection is a four point connection technique that allows current to be injected into a battery through a first pair of connectors attached to the battery terminals, while a second pair of connectors is attached to the battery terminals in order to measure the voltage across the terminals. Often modified alligator-type clamps, with the jaws electrically isolated from each other, are used to make the connections. In that case, each electrical contact is even more tenuous because only a single jaw provides each connection. Examples of such circuitry and connectors are shown in U.S. Pat. Nos. 2,267,826; 4,505,032; 5,234,359; 5,574,355; 5,592,093; 5,744,962; 5,753,920; 5,757,192; 5,831,435; 5,862,515; 5,886,530; and 5,901,002.
Furthermore, testing a battery using a Kelvin connection to the prior-art side-terminal adapters, instead of directly to the terminals themselves, is less accurate. An increase in measurement error occurs because the terminal adapters provide additional resistance in the current path, thereby affecting the measurement.
Thus, these prior electrical connectors often provide tenuous mechanical and electrical connections to the battery. Likewise, battery tests are prone to inaccuracy when standard side-terminal adapters are used to make Kelvin connections.